Two Tracks – Games

What you just felt

Doing two things at once almost always costs something. Specialists call the drop-off dual-task cost: you compare how well something goes on its own with what is left once a second task is added. That is exactly what you have just measured on yourself.

What matters is less how much you lost than where. The brain does not spread its attention evenly; it sets priorities – and does not consult you about them. Under pressure, most people protect the movement and give way on the thinking. This is called “posture first”. It is the sensible order, because an arithmetic slip does not hurt, whereas a fall does.

It can go the other way round, though. When someone protects the thinking and lets their walking slip – “posture second” – it gets risky. In Parkinson’s disease this pattern is found more often, and it explains part of those falls that happen precisely when someone is talking, carrying something or working something out at the same time.

Sources: Plummer, P., & Eskes, G. (2015). Measuring treatment effects on dual-task performance: A framework for research and clinical practice. Frontiers in Human Neuroscience, 9, 225. · Woollacott, M., & Shumway-Cook, A. (2002). Attention and the control of posture and gait: A review of an emerging area of research. Gait & Posture, 16(1), 1–14. · Yogev-Seligmann, G., Hausdorff, J. M., & Giladi, N. (2008). The role of executive function and attention in gait. Movement Disorders, 23(3), 329–342. · Bloem, B. R., Grimbergen, Y. A. M., van Dijk, J. G., & Munneke, M. (2006). The „posture second“ strategy: A review of wrong priorities in Parkinson’s disease. Journal of the Neurological Sciences, 248(1–2), 196–204.

Why this matters in physiotherapy

Walking feels automatic, but it is not. It calls for continuous attention, planning and control – exactly what the thinking task calls for too. That is why the two get in each other’s way. Reviews pooling many studies all show the same picture: anyone who calculates, memorises or holds a conversation while walking walks more slowly and less evenly – even as a healthy young person. The effect grows clearer with the years, after a stroke, in Parkinson’s disease, in multiple sclerosis, and in the weeks after a concussion.

One of the best-known observations on this is strikingly plain. In 1997 a Swedish group described the sign “stops walking when talking” in the Lancet: older people who came to a halt as soon as they were spoken to while walking went on to fall considerably more often over the following months than those who kept going. Stopping is not rudeness – it is the only remaining solution when two tasks no longer fit side by side.

That is why, in the clinic, we look not only at how somebody walks but at how somebody walks while doing something else: the timed up-and-go test with an added task, walking while counting backwards, walking with a glass of water. And it is why we sometimes practise movement deliberately together with a thinking task – in everyday life, after all, it never comes alone. More on this in our guides on fall prevention, on Parkinson’s disease and on concussion.

Sources: Lundin-Olsson, L., Nyberg, L., & Gustafson, Y. (1997). „Stops walking when talking“ as a predictor of falls in elderly people. The Lancet, 349(9052), 617. · Al-Yahya, E., Dawes, H., Smith, L., Dennis, A., Howells, K., & Cockburn, J. (2011). Cognitive motor interference while walking: A systematic review and meta-analysis. Neuroscience & Biobehavioral Reviews, 35(3), 715–728. · Verghese, J., Lipton, R. B., Hall, C. B., Kuslansky, G., Katz, M. J., & Buschke, H. (2002). Abnormality of gait as a predictor of non-Alzheimer’s dementia. New England Journal of Medicine, 347(22), 1761–1768. · Montero-Odasso, M., Verghese, J., Beauchet, O., & Hausdorff, J. M. (2012). Gait and cognition: A complementary approach to understanding brain function and the risk of falling. Journal of the American Geriatrics Society, 60(11), 2127–2136. · Muir-Hunter, S. W., & Wittwer, J. E. (2016). Dual-task testing to predict falls in community-dwelling older adults: A systematic review. Physiotherapy, 102(1), 29–40. · Shumway-Cook, A., Brauer, S., & Woollacott, M. (2000). Predicting the probability for falls in community-dwelling older adults using the Timed Up & Go Test. Physical Therapy, 80(9), 896–903.

What practice achieves – and what it does not

Two things have to be kept apart here, and they are often thrown together.

One is “brain training” – and its record is sobering. Practise thinking games on a screen and you will reliably get better: at that game. The step beyond does not happen. Large reviews agree that pure working-memory training does not carry over to intelligence, everyday functioning or general thinking ability; a Cochrane review of computerised training in cognitively healthy older people likewise found no dependable benefit. So if somebody is selling you an app that will make your brain younger: the evidence does not support that.

The other is the dual task – and there the picture is better, though not unlimited. When movement and a thinking task are practised together, performance under dual load improves; reviews in older adults show this fairly consistently. Programmes that enrich movement with a cognitive demand tend to do better than movement alone. The effects are moderate, however, the studies are built very differently from one another, and whether fewer people actually end up falling as a result is not thereby answered. For fewer falls, what remains best evidenced is regular training with a strong balance component, over months, and demanding enough.

And now the catch for this game here. What you practise gets better – and not much else does. Here you are practising tapping a beat with your finger while thinking. That will make you better at tapping and thinking. Whether it makes your walking safer is precisely what has not been shown: fingers are not legs, and your balance is not at stake in front of a screen. If you want the carry-over, you have to take the second task to where it should work – that is, into the movement. That is what the standing option here is for, and it is what we are for in the clinic: there the difficulty can be matched to your safety, rather than the other way round.

Sources: Simons, D. J., Boot, W. R., Charness, N., Gathercole, S. E., Chabris, C. F., Hambrick, D. Z., & Stine-Morrow, E. A. L. (2016). Do „brain-training“ programs work? Psychological Science in the Public Interest, 17(3), 103–186. · Melby-Lervåg, M., Redick, T. S., & Hulme, C. (2016). Working memory training does not improve performance on measures of intelligence or other measures of „far transfer“: Evidence from a meta-analytic review. Perspectives on Psychological Science, 11(4), 512–534. · Gates, N. J., Rutjes, A. W. S., Di Nisio, M., Karim, S., Chong, L.-Y., March, E., Martínez, G., & Vernooij, R. W. M. (2019). Computerised cognitive training for maintaining cognitive function in cognitively healthy people in late life. Cochrane Database of Systematic Reviews, (3), CD012277. · Wollesen, B., & Voelcker-Rehage, C. (2014). Training effects on motor–cognitive dual-task performance in older adults: A systematic review. European Review of Aging and Physical Activity, 11(1), 5–24. · Gheysen, F., Poppe, L., DeSmet, A., Swinnen, S., Cardon, G., De Bourdeaudhuij, I., Chastin, S., & Fias, W. (2018). Physical activity to improve cognition in older adults: Can physical activity programs enriched with cognitive challenges enhance the effects? A systematic review and meta-analysis. International Journal of Behavioral Nutrition and Physical Activity, 15, 63. · Sherrington, C., Fairhall, N. J., Wallbank, G. K., Tiedemann, A., Michaleff, Z. A., Howard, K., Clemson, L., Hopewell, S., & Lamb, S. E. (2019). Exercise for preventing falls in older people living in the community. Cochrane Database of Systematic Reviews, (1), CD012424. · Ngandu, T., Lehtisalo, J., Solomon, A., Levälahti, E., Ahtiluoto, S., Antikainen, R., … Kivipelto, M. (2015). A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): A randomised controlled trial. The Lancet, 385(9984), 2255–2263.

What this game is not

It is not a measuring instrument. Between your finger and the number on the screen sit a touchscreen, a browser and an operating system – together easily several dozen milliseconds, and different from device to device. So compare your own rounds with one another at most, and even then only on the same device.

On top of that: there are no norms here, no percentiles, no cut-offs – unlike in tested procedures. And because the dual task always comes last, its result contains some practice and some fatigue as well. Which of the two single tasks comes first is decided at random, but that only offsets part of it.

When it is worth taking seriously: when in everyday life you have to stop as soon as somebody speaks to you. When you have to concentrate on walking in order to walk. When you have fallen recently, or nearly fallen. That belongs not in a browser game but in a proper assessment – with us or with your doctor.

Sources: Repp, B. H. (2005). Sensorimotor synchronization: A review of the tapping literature. Psychonomic Bulletin & Review, 12(6), 969–992. · Plummer, P., & Eskes, G. (2015). Measuring treatment effects on dual-task performance: A framework for research and clinical practice. Frontiers in Human Neuroscience, 9, 225.

Sources are listed verbatim and in their original language; only descriptive additions are translated.